Fig 1: Quantitative real-time RT-PCR analysis. a, b Bacteria were grown overnight in TSB and qRT-PCR analyses were performed on selected genes, a katG gene or b fba gene in wild-type F. novicida, Δfba mutant, and fba-complemented (Cp-fba) strains. For each gene, the transcripts were normalized to helicase rates (FTN_1594). c Catalase activity assay was realized at 570 nm, using the Catalase Assay Kit (ab83464; Abcam). The assay was performed according to manufacturer’s recommendation. Each assay was performed on two independent protein lysates. The average of OD570 ± SD was recorded for wild-type F. novicida and the Δfba mutant. The catalase activity recorded in the ∆fba mutant was significantly lower than that recorded in the wild-type strain (**p < 0.01). d J774.1 cells were infected for 24 h with wild-type F. novicida (WT) and Δfba mutant. Total RNA was analyzed by quantitative RT-PCR with katG and fba gene. For each gene, the transcripts were normalized to helicase rates (FTN_1594) (**p < 0.01). e J774.1 cells were infected for 24 h with wild-type F. novicida (WT) and Δfba mutant in DMEM supplemented with glucose and glycerol (25 mM). The supernatants were analyzed by ELISA to detect the amounts of IL-6 produced at 24 h in pg mL−1. f Intracellular bacterial multiplication of wild-type F. novicida (WT) and ∆fba mutant was determined at 24 h, in the infected J774.1 cells used for the IL-6 dosage, as a control. (**p < 0.01). a–c mean and SD of three independent experiments are shown; d–f each assay was repeated at least three times. Mean and SD of three wells of one typical experiment are shown. p-values were determined by the two-tailed unpaired Student’s t-test